Doubly prestressed roof-ceiling construction wiht grid flat-soffit for extremely large spans

ABSTRACT

The doubly prestressed roof-ceiling construction with grid flat soffit for extremely large-span is prefabricated element intended for assembling roofs of extremely large-span buildings with flat soffit. The construction comprises the grid soffit construction ( 1 ) and the upper concrete girder ( 2 ) of a modified “T” shaped or of an inverse “V”-shaped cross section, interconnected by slender steel pipe-rods ( 3 ) that stabilize the upper girder ( 2 ) against lateral buckling. The empty openings within elements of the horizontal grid ( 1 ) are fulfilled with plates ( 6 ) wherewith a flat soffit is achieved. The construction is prestressed by the double prestressing. The grid-soffit ( 1 ) is prestressed centrically and the upper girder ( 2 ) is prestressed by the wedge ( 5 ) at the midspan.

TECHNICAL FIELD

The present invention relates to the construction of the roofs ofindustrial building or other similar buildings of prestressed,reinforced concrete and in particular some steel parts become integralparts of the structure. The field of the invention is described in IPCClassification E 04 B 1/00 that generally relates to constructions orbuilding elements or more particularly group E 04 C 3/00 or 3/294.

BACKGROUND ART

The present invention relates to a specific roof-ceiling construction ofthe original conception and shape. The technical problem that is to besolved by this application is assembling method of constructing roofswith flat soffit over extremely large spans (more than 50 m) whereby theroof-ceiling construction solves both the roof and the finished flatsoffit simultaneously. In practice, roof constructions over extremelylarge spans are mostly unique constructions carried out on specialprojects and usually constructed completely on the site.

The technical problem of this invention, if defined as a task, is tofind out an assembling method of constructing roof-ceiling constructionsover extremely large spans, suitable for serial pre-fabrication, as analternative to customary practice of constructing unique constructions.

The technical problem that is to be solved is to divide the hugeconstruction, unsuitable for transport and handling, into plurality ofsmall assemblies that can be prefabricated and transported and assembledon site into the extremely large-span construction unit with flatsoffit. As a part of the present invention some partial technicalproblems are to be solved such as; forming the light assembly-ablesoffit, lateral stabilization of the upper longitudinal girder over alarge span without increasing its mass through increasing its lateraldimensions, longitudinal and transversal interconnecting of the assemblyelements into the entirety. All the other solutions that are part ofthis invention are related to the practical use of the constructionitself, including the advantages described in HR-P20000906A that theseconstructions offer when compared to other customary roof and ceilingconstructions.

The present invention includes the basic concept of the construction andprestressing principles disclosed in HR-P20000906A under the name“doubly prestressed composite roof-ceiling constructions”. Thejust-mentioned application discloses constructions with flatplate-soffit over mostly used big spans up to 30 m. Such constructionswith full-plate-ceilings are not suitable for spans bigger than 30 mbecause at spans larger than that the full-plate soffit becomes tooweighty what modifies many assumptions which are the basis of the workof the construction at smaller spans making this constructioninapplicable. For instance, the distinctly thin full plate, at spans upto 30 m, has the overall depth of 5 cm what provides enough depth foranchoring interconnecting bars into the soffit plate concrete to ensurethem from pooling-out. The full, thin soffit-plate, if applied at largespans, requires an increment of depth because its connection to theupper longitudinal construction near supports become too week to bearsignificant amount of shear. However, at very large spans the soffitplate should have an increased depth what would increase its self-weightand change the concept of its working mechanism based on the lightsoffit which deflects upwards due to rotation of ends of theconstruction. Moreover, constructions with full-plate soffit and a spanover 50 m would be too long for transport and there would appear aproblem of interconnecting smaller assemblies into the soffit plateentirety. Even if possible, carrying-out of such constructions wouldrequire pre-tensioning and concreting in site what may be uneconomic.

The present invention relates to a construction that is similar to theconstruction described in HR-P20000906A and solves its applicability toextremely large spans, allows prefabrication of smaller assemblies thatare assembled on site into the entirety and provides the assemblingsoffit formed by inserting light-plates into the openings of thegrid-soffit reducing the weight of the entire construction before beinghoisted.

No other similar constructions with flat soffit, except abovementionedones are known to me.

DISCLOSURE OF THE INVENTION

The prestressed roof-ceiling construction for extremely large spans ispre-fabricated, one-way bearing construction, comprising grid flatsoffit (1), the upper girder (2) and a plurality of space arrangedstabilizing rods (3), attended for constructing buildings with extremelylarge spans solving both the roof and the ceiling with flat soffitsimultaneously.

The object of the invention is, on contrary to customized unique largespans constructions establishment of a simpler and more economic, withadaptable spans, assembling system for constructing buildings withextremely large spans of pre-fabricated elements that are assembled intolarge segments of the construction—units that can be hoisted andinterconnected into the large roof-ceiling with continuous flat soffit.The assembled light-grid, flat-soffit construction replaces a full-platesoffit whereby the flat soffit is achieved by inserting plurality oflight plates into the openings within grid elements after theconstruction is assembled.

In some way it is an improvement of the likely constructions with flatsoffit disclosed in HR-P20000906A that provides a reasonable applicationof the same principle to extremely large spans (over 50 m).

The auxiliary technical solutions that are part of the presentconstruction are; solutions that provide reduction of the self-weight ofthe entire construction to be applicable on extremely large spans,solution of stabilizing the upper girder (2) against lateral bucklingwithout enlarging the mass of the construction by increasing lateralmoment of inertia of its cross section, the solution of simple andpractical interconnecting of pre-fabricated assemblies (1.1) of the gridconstruction (1) (in one embodiment the grid construction is made ofsteel tubes with a light foam filler and conductors that keep the innercable distances) and the solution of forming the flat-soffit plane byinserting plurality of light plates (4) into openings within elements ofthe grid construction.

Generally, a solution of the static system for such constructions onextra large spans is achieved with slender pipe-bars (3) that do nottransmit neither the bending moments between the upper girder (2) andthe soffit grid (1) nor they are capable to transmit considerable axialforces and consequently can not bend the longitudinally slender grid (1)whereby the pipe-rods (3) are utilized simultaneously to stabilize theupper girder (3) against lateral buckling and to ensure stability of thegrid plane itself during prestressing.

The cross sections of the upper girder (2) are of the original shapes asshown in FIG. 2 in both Version1 and Version2 which are constructed insuch a manner to be light and adapted for the abovementioned function tostabilize the upper girder (2) which is braced by pipe-rods (3) anchoredinto the grid (1), substantially rigid in the horizontal plane.

DESCRIPTION OF DRAWINGS

FIG. 1. is an isometric view of the construction with an inverse “V”cross section shape of the upper girder.

FIG. 2. is the cross section of the construction with an inverse “V”cross section shape.

FIG. 3. is the cross section of the construction of an alternateembodiment with “T” cross section shape.

FIG. 4. is an isometric view of the disassembled construction showingits assembly parts.

FIG. 5. illustrates the disassembled construction and the method ofassembling.

FIG. 6. is the connecting detail for grid elements if the steel grid isapplied.

FIG. 7. is a detailed view of the steel grid element joint.

FIG. 8. is the cable conducting detail for longitudinal post-tensioningconnection of grid elements when steel grid is applied.

DESCRIPTION OF THE PREFERED EMBODIMENT

In following, the preferred embodiment with the upper girder (2) of aninverse “V”-shaped cross-section, shown by the isometric view in FIG. 1,is described (as shown also in FIG. 2.). In one another embodiment theconstruction may comprise the T-shaped cross-section upper girder (2)(as shown in FIG. 3). In both variants the grid soffit (1) can be madeof steel tubes or of prestressed concrete independently on the choice ofthe upper girder cross-section.

The global bearing unit of the construction that is thereafter assembledat the site is shown in FIG. 1. It comprises the distinctly widegrid-assemble construction (1) and the upper girder (2) of the inverse“V”-shaped cross section interconnected by slender pipe-rods (3). Thevertically slender horizontal grid construction (1) is chosen of suchdimensions that its constitutive parts, illustrated in FIG. 4, can beeasy transported to the site and can cover the great part of thesite-view of the building at once when assembled into the global bearingunit.

FIG. 1 is an isometric view to the construction in a variant with theupper girder (2) of inverse “V”-shaped cross-section and with the steelgrid (1) applied and FIG. 4 shows the same construction butdisassembled. The upper girder (2) is made of two reinforced concreteparts, elements (2.1), prefabricated in a building element factory andtransported to the construction site. The grid (1) elements are alsomanufactured in the factory, of welded steel tubes, in smaller-sizeparts (1.1) such that the elements can be easily transported to theconstruction site. Short and stiff pipe-rods (4) used near the supportsto interconnect the grid (1) and the upper girder (2) are inbuilt intothe upper girder (2) ends as their integral part. Interconnecting steelpipe-rods (3) are separate elements.

At the constructing site the horizontal plane is to be prepared withplurality of supports on which smaller parts (1.1) of the grid areleaned before being assembled into grid entirety (1), the unit that withits width and length belongs to the bearing area of one assembled uppergirder (2) as it is illustrated in FIG. 4 and FIG. 5. In bothdirections, longitudinally and laterally elements of the girder areinterconnected into grid-entirety (1) by details illustrated in FIG. 6.FIG. 7 shows the longitudinal cut-section of the same connecting detailfrom which it is seen that one end of the steel tube (10) comprises theother inside-welded smaller tube (11) that is utilized to be insertedinto an adjacent tube (12) whereby thereafter both tubes (10) and (11)are welded around their contact perimeter by the weld (13). In that waythe entire soffit grid is assembled at which in following the wholeconstruction is formed.

At the midspan a temporarily supporting frame (9) is positioned. Bothhalves (2.1) of the upper girder are then positioned on the grid and areturned each to another with their ends that are to be connected leanedat the midspan on the supporting frame (9) whereby their opposite ends,with incorporated stiff steel-pipe legs (4) were laid on the gridelements as it is shown in FIG. 5 and FIG. 6. Both upper girder halves(2.1) being in that way leaned and fixed are thereafter connected to thegrid (1) by welding rods (3) and rods (4) to the grid elements. Shortand stiff legs (4) that were incorporated to the upper girder (2)concrete during prefabrication after being welded become the truss-likeconsole supports of the upper girder (2) fix-end connected to the grid.The construction is thereby still disconnected in the midspan of theupper girder (2) but the temporarily supporting frame can be removed.

In the longitudinal, bearing direction of the construction because ofpresence of high tension in grid elements grid (1) is prestressedcentrically with cables (7) conducted through grid elementslongitudinally as it is shown in FIG. 8. The longitudinal grid elementsmade of steel tubes are supplied by inbuilt conductors (8) that are usedto provide the centric position of the cables in the center of gravityof the cross section inside of tubes. The hollow longitudinal gridelements after being prestressed with cables positioned inside arethereafter fulfilled with expanding foam or with extremely lightweightconcrete, dependably on the degree of prestressing and the stability ofthe grid during prestressing whereby the fulfill material is utilized toprotect cables from corrosion and the bond continuity between cables andtubes is ensured. Stability of the grid construction itself duringcentric prestressing must be controlled with appropriate calculationswhereby it is necessary to consider the self-weight and restrainingactivities of the construction against grid to buckle upwards.

During prestressing of the grid elements (1), the upper girder (2) isdisconnected at the midspan whereby both the separated halves (2.1)stand on their own legs (3) and (4) being welded to the grid (1). Afterprestressing of the grid (1) is done, the upper girder (2) is subjectedto another prestressing, by the wedge driven into a special detailbetween the two separated halves (2.1), by the method disclosed inapplication HR-P200006A under the name “Doubly prestressed roof-ceilingconstruction with flat soffit for large spans”. Prestressing of the grid(1) ensures presence of permanent compression inside its longitudinalelements under all applied loads as well as all interconnected joinedgrid parts (1.1) into the grid-entirety (1).

In one another embodiment the “T”-shaped cross section upper girder (2)may be applied with the same steel-tube grid. In that case all thecarrying-out procedure remains the same. If now in these two variantsthe steel-tube grid is replaced by the concrete one, the two additionalvariants appear.

As a second embodiment the variant with “T”-shaped or inversed “V” crosssection upper girder (2) is taken, with the grid (1) of prestressedconcrete elements. The elements (1.1) as the assemblies of thegrid-soffit (1) are assembled and connected to the entirety in the samemanner as in previous variant at the construction site also by means ofthe same temporarily connection.

The grid elements in concrete variant are solid-ones, with centricallyincorporated conductors (7), supplied by the same tube connectors attheir ends for temporarily assembling of the grid. The differencebetween joints of concrete and steel variants of the grid is only indetails that are adapted to concrete with incorporated tubes at ends ofelements that are to be joined. The concrete variant is not emphasizedor described because it contains itself nothing new.

In all variants, after the large-size unit of the roof-ceilingconstruction was completed and prestressed at site the construction ishoisted and joined to adjacent one forming a continuous grid soffit. Thegrids of the large-size units of the constructions are therebyinterconnected to another such units in the same manner as smaller parts(2.1) were interconnected into grid large-unit (1).

Finally the soffit plane is closed by inserting of light plates (6) intoopenings within grid elements such that a large continuous flat-soffitis achieved.

1. Doubly prestressed roof-ceiling construction with grid flat-soffitfor extremely large spans, characterized in that comprises the soffitgrid (1), the upper girder (2) and interconnecting pipe-rods (3).
 2. Thegrid construction of the flat soffit as claimed in claim 1,characterized in that is assembled at the site of smaller prefabricatedparts (1.1), made of steel tubes or prestressed concrete, whereby afterassembling the flat soffit is formed by inserting lightweight platesinto openings between grid elements.
 3. The grid construction of theflat soffit as claimed in claim 1, characterized in that bothtransversal and longitudinal connections of elements (1.1) of the grid(1) are temporarily fixed by sticking adjacent ends (10) into oneanother, prior to being welded, whereby the longitudinal connections arehardened by prestressing.
 4. The grid construction of the flat soffit asclaimed in claim 1, characterized in that longitudinal interconnectionof soffit-grid elements is achieved by prestressing the grid (1) withcables (7) protruded through conductors (8) positioned in tubes that arethereafter fulfilled with hard expanding foam or lightweight concrete toensure anticorrosive protection and thermo insulation of the ceiling. 5.Doubly prestressed roof-ceiling construction with grid flat-soffit forextremely large spans, according to the claim 1 characterized in thatthe upper girder (2) and the steel soffit-grid are interconnected bywelding steel pipe-rods (3) along the whole length of the constructionwhereby near the upper girder (2) is supported by the grid (1) throughelements (4) inbuilt into upper girder (2).
 6. Doubly prestressedroof-ceiling construction with grid flat-soffit for extremely largespans, according to the claim 1 characterized in that pipe-rods (3)laterally supported by the horizontal grid (1) stabilize the uppergirder (2) against buckling.